1. Field of the Invention
The present invention relates to an optical interface for an antenna and, more specifically, relates to an interface having layered characteristics for processing and optically coupling outputs from an array of antenna elements.
2. Description of the Related Art
A conventional type of active antenna array transceiver is illustrated in prior art FIG. 1. A transceiver as illustrated in prior art FIG. 1 is required for each of the antenna elements of an array of antenna elements. Each antenna element 110 is connected thereto by a transmit/receive duplexer 120. The output of the transmit/receive duplexer 120 connects a receive signal through a low noise amplifier 130 to a port of a transmit/receive switch 140. Another port of a transmit/receive 140 connects a signal to be transmitted through a power amplifier 150 to the transmit/receive duplexer 120. The transmit/receive switch 140 is a double throw single pole switch having its pole connected through a variable phase shifter control 160 and a variable attenuator 170. The transmit/receive switch 140 is controlled to transmit a signal from the variable phase shifter 160 through the power amplifier 150 to the antenna element 110 or, conversely, to receive a signal from the antenna element 110 through the low noise amplifier 130 and the variable phase shifter 160. Therefore, both the variable phase shifter 160 and the variable attenuator 170 are bi-directional. As customary to reduce size and weight, the transceiver illustrated in FIG. 1 is designed to have a minimum number and size of components for interface to each antenna element of the antenna array.
Active phased array antennas are capable of generating an electronically movable radar beam. However, active phased array antennas are very heavy and complex and, thus, have limited utility. Conventionally, a shielded cable or waveguide is necessary for connection to each antenna element of an active phased array antenna. Furthermore, processing circuitry for interface to the active phase array antenna is bulky. Additionally, connection of sometimes close to a thousand shielded cables to the processing circuitry is tedious, error prone and difficult to manufacture and repair. Thus, a small and low cost interface to an antenna array is needed.